Spain is famous for its weather, Benidorm, Spanish food, it's football team, Barcelona, and basically being a rather sunny place overall â none of these descriptions are incorrect, and in fact they are all entirely true!
As the temperature of the air increases its density decreases. Therefore the thrust produced by the engine decreases. As the air pressure increases, its density increases, causing thrust produced by the engine to increase. Altitude has a double effect on thrust. As the altitude increases, the air becomes colder and denser, up to the beginning of stratosphere. This causes the thrust to increase.
Re: temperature rise. Temperature rise is the air vent temperature minus the return air temperature. It is often called Delta T or (change in temperature). Most all furnace data plates tell you what the max acceptable temperature is. If you results are higher than that you may have a dirty filter, undersized duct or some other deficiency. 30 to 50 degrees is typical. Depending or the type and age of furnace this can vary.